# define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>


int main() {
	double sum = 0, sum_1 = 0;
	int i = 5;
	while (i--) {
		scanf("%lf", &sum_1);
		sum += sum_1;
	}
	printf("%.2lf", sum / 5.0);
}
